The hot topic at the Paris Air Show, which wrapped up last week, was the battle between Boeing’s state-of-the-art 787 Dreamliner and Europe’s answer to that plane: Airbus’ brand new A350, which embarked on its first test flight earlier this month.

That war may be fought over how many seats can be crammed side by side on an aircraft. Yes, we all know about shrinking legroom, but the next time you board a flight, count the number of seats that stretch across a single row.

Qatar Airways flight attendant Ilham Zimbi did just that on a brand new 787 Dreamliner. She showed off the airline’s new plane at the Paris Air Show. Her count goes to nine seats across, which is fairly standard for wide body planes. It’s as much as Boeing’s 787 has room for.

Airbus’ Christopher Emerson says that’s where his company’s new A350 has an advantage.

“The A350 is a larger airplane,” says Emerson.

Indeed, it’s a few inches wider, which means -- by shaving one inch off an 18-inch seat -- the A350 can fit ten passengers across on a type of plane that typically seats nine.

“One inch in your seat does make a difference,” says Emerson.

It’s also possibly less noticeable than reduced legroom. Aviation analyst Ernest Arvai says narrower seats are the latest trend for airlines that want to squeeze more people into the same space.

“So if you thought seats were tight before? Wait a couple of years, because these new airplanes will be even tighter,” says Arvai. To cram in that extra seat, he says aircraft manufacturers shrink aisles, armrests and even the walls of the airplane. That’s because the economics of air travel are measured in “CASMs”, or Cost Per Air Seat Mile. It’s how much an airline spends to transport each passenger.

“So every time you put more seats in the airplane the cost per seat mile goes down,” says Arvai.

As a result, airlines also make more profit. So is Airbus’s extra seat is a threat to Boeing’s new Dreamliner?

“Are we scared?” asks Boeing’s Randy Tinseth. “Absolutely not.” He says at ten seats across, the Airbus A350 will be a grueling ride for long haul, ten to twelve hour flights.

“Frankly, I don’t know if there’s a narrow enough seat to fit ten abreast in that airplane,” says Tinseth. “You have to have really, really narrow aisles or you don’t have armrests.”

That said, Boeing is already in the ten-seater game. Most new orders for the company’s tried and tested 777 aircraft are for ten seats across, and planes are getting even tighter. The latest layouts for Airbus’ jumbo jet, the A380, are for eleven across.